C Minor chord (Cm) on the guitar fretboard

The C Minor chord (Cm) is made of C (the root), Eb (minor third) and G (perfect fifth). The fretboard shows every one of them across the neck in standard tuning (E A D G B E), and plays them back so you can hear the chord.

The minor triad swaps the major third for a minor third and keeps the fifth, which is what gives it a darker colour. Each of its three notes repeats across the neck, so the shape you see is a map of every place it can be played. Flatten its fifth and you reach the diminished triad; stack a seventh and you reach the minor seventh.